Search Results (16)

The blowout preventer (BOP) is the most important and the last line of safety defense in drilling engineering. Once a blowout occurs and the BOP fails, engineers will lose control of the entire wellbore pressure, and combustible fluids in the formation will continuously sprayed out, which can easily cause huge losses of life and property. At present, reliable and highly recognized emergency measures for BOP failure are lacking. Therefore, we propose a plugging method after the failure of the BOP that can maintain good control within the secondary well control. Numerical and experimental results indicate that using a small-to-medium displacement (1–2 m³/min) during the early stage of plugging and applying multiple plugging and killing cycles significantly improves plugging stability and killing efficiency. PEEK (polyether ether ketone) was selected as the bridging material for field plugging tests on full-scale blowout preventers, verifying its sealing effectiveness at pressures up to 80 MPa. Subsequently, the CFD–DEM was used to simulate the well killing process after plugging. This study mainly focused on the transportation of particles in a pipeline and the analysis of the process of well killing after plugging. The research results indicate that PEEK demonstrates sufficient pressure-bearing capacity under real blowout conditions. Also reveal that PEEK’s exceptional wear resistance and impact strength help maintain sealing stability during repeated particle–wall collisions, effectively reducing secondary erosion and prolonging the operational lifespan of temporary plugging structures. After undergoing six high-pressure tests of 70 MPa and two high-pressure tests of 80 MPa within 25 min, it remained intact. Both cylindrical and spherical particles can smoothly pass through the storage tank and double-bend pipeline at different displacements. Considering the retention effect of the plugging material, it is recommended to use 1–2 m³/min of pumping the plugging material at medium and small displacements in the early stage of plugging. During the process of plugging and killing, it is recommended to use alternating plugging and killing across multiple operations to prevent further blowouts to achieve the best plugging and killing effect. Full article

This article offers a concise overview of the best practices for safety in offshore oil and gas operations, focusing on the risks associated with various types of equipment, particularly on the risk of fire. It identifies specific machinery and systems that could pose hazards, assesses their potential impact on safety, and explores conditions that may lead to accidents. Some of the largest accidents were analyzed for their associations with fire hazards and specific equipment. Two primary regulatory approaches to offshore safety are examined: the prescriptive approach in the United States (US) and the goal-oriented approach in Europe. The prescriptive approach mandates strict compliance with specific regulations, while in the goal-oriented approach a failure to adhere to recognized best practices can result in legal accountability for negligence, especially concerning human life and environmental protection. This article also reviews achievements in safety through the efforts of regulatory authorities, industry collaborations, technical standards, and risk assessments, with particular attention given to the status of Mobile Offshore Drilling Units (MODUs). Contrary to common belief, the most frequent types of accidents are not those involving a fire/explosion caused by the failure of the Blowout Preventer (BOP) after a well problem has already started. Following analysis, it can be concluded that the most frequent type of accident typically occurs without fire and is due to material fatigue. This can result in the collapse of the facility, capsizing of the platform, and loss of buoyancy of mobile units, particularly in bad weather or during towing operations. It cannot be concluded that accidents can be more efficiently prevented under a specific type of safety regime, whether prescriptive or goal-oriented. Full article

Background: Mini dental implants (MDIs) are alternatives to support an overdenture when a standard diameter implant cannot be placed due to lack of bone volume. They reduce the need for invasive bone grafting and lower the barrier for treatment. Aim: This prospective study reports on implant and patient-centered outcomes of flaplessly placed, early loaded MDIs supporting horseshoe-shaped maxillary overdentures after 7 years of function. Materials and Methods: Patients with a CBCT-confirmed thin alveolar crest received 5–6 one-piece MDIs using mentally guided flapless surgery. The conventional denture was relined and MDIs were provisionally loaded within one week. After 6 months the non-splinted MDIs were actively loaded with a horseshoe overdenture. Implant and prosthetic survival, peri-implant health (PPD and BoP) and patient-related outcomes using OHIP-14 and Subjective Masticatory Evaluation were assessed after 7 years. Results: 185 MDIs were placed in 14 females and 17 males. During provisional loading, 32 MDIs were lost, and 17 replacements were required in 16 patients. In total, 170 out of 202 totally placed MDIs were supporting 29 overdentures after 6 months. Cumulative implant failure increased from 15.8% at the moment of active loading to 34.7% at 7 years. After 7 years, 76% of the initially placed overdentures remained functional, mean PPD was 3.48 (SD 0.86), BoP was 0.20 (SD 0.40) and peri-implantitis incidence was 0.9%. The total OHIP-14 was reduced from 21.3/56 (SD: 13.1) preoperatively to 15.6/56 (SD 12.8) at provisional loading (p > 0.1) and 7.3/56 (SD 6.7) at final loading (p = 0.006), and it remained unchanged up to 7 years at 6.57/56 (SD: 8.92) (p > 0.5). Conclusions: Maxillary MDIs provide an acceptable treatment option in patients with deficient bone volume that cannot or refuse to be treated with bone grafting. Despite one third of the MDIs being lost, remaining MDIs had good peri-implant health, prosthetic success was 71% and Oral Health Related Quality of Life was beyond expectations. Full article

China is actively advancing offshore oil and gas exploration and development, focusing on addressing the technical challenges associated with resource extraction in shallow waters. The shallow-water subsea tree development model has gradually been applied in such environments, alleviating some construction difficulties. However, it still poses well control risks that require systematic analysis and quantitative evaluation. Given that the blowout preventer (BOP) is located on the platform and the shallow-water subsea tree is only used during certain drilling stages, this study divided the drilling process into two phases: the first three sections and the fourth section. Based on the “man–machine–material–environment” analytical framework and an improved system-theoretic process analysis (STPA), a control model for the construction phases was developed. Fault tree analysis (FTA) was then employed to identify comprehensively the potential risks from the platform to the wellbore in both phases. Subsequently, the decision-making trial and evaluation laboratory (DEMATEL) method were used to assess quantitatively the well control risks. Using the average weight as the evaluation criterion, high-risk factors exceeding the average weight in each phase were identified. The results indicate that in the shallow-water subsea tree development model, well control risks in the first three drilling sections primarily stem from human errors and equipment failures, while risks in the fourth section are mainly caused by damage to the subsea tree itself. The identified risk factors provide a theoretical basis for enhancing well control safety management in the shallow-water subsea tree development model. Full article

Background: Dental implant rehabilitation has significantly advanced prosthodontics by providing a reliable, long-lasting solution for missing teeth. This systematic review compares the clinical, technical, and biological outcomes of cemented versus screw-retained single dental implant restorations based on randomized clinical trials (RCTs). Materials and Methods: This review included recent human and in vitro studies focusing on the keywords “cemented vs. screw-retained” and “dental implant”. Eight studies met the inclusion criteria, which investigated parameters, including implant survival rate, bleeding on probing (BOP), probing depth, plaque index, marginal bone loss (MBL), cytokine concentrations, mechanical complications, esthetic outcomes, patient satisfaction, treatment time, and technical failures. Results: The primary outcomes, BOP and MBL, did not statistically differ between cemented and screw-retained implants (p-values for MBL and BOP are 0.5813 and 0.8093, respectively). The reviewed studies, including RCTs, split-mouth studies, and clinical evaluations, demonstrated comparable clinical, technical, and biological outcomes between the two restoration methods. Conclusions: Screw-retained and cemented dental implant restorations exhibit similar clinical, technical, and biological outcomes. Screw-retained restorations offer advantages such as retrievability, ease of repair, and predictable passive fit, while cemented restorations provide superior esthetics. The risk of peri-implant complications due to residual cement in cemented restorations must be considered. Future research should explore long-term stability and the impact of different prosthetic protocols on peri-implant health. Full article

A landing string is directly exposed to seawater and subjected to significant stresses and complex deformations due to environmental loads such as wind, waves, and ocean currents during the phase in which the drill string carries the casing to the wellhead. Meanwhile, as the water depth increases, the weight of the drill string increases, leading to an increase in the tensile loads borne by the drill string, which can easily cause a risk of failure. Therefore, a quasi-static load calculation model for the deepwater insertion of the pipe column was established. Using the Ansys platform, simulations were conducted for average wind, wave, and ocean current conditions during different months throughout the year. The ultimate loads and stress distributions of the string were derived from theoretical analyses and numerical simulations for different operational sea states, and the suggested safe operating window and desired BOP trolley restraining reaction force for landing strings’ lowering are given according to the existing industry standards. The research findings can help in identifying the potential risks and failure modes of the deepwater landing string under different working conditions. Full article

Objectives: The aim of this systematic review was to analyze the effect of keratinized mucosa (KM) on different peri-implant health-related parameters and on patient-reported outcome measures (PROMs). Material and methods: Randomized controlled trials, cohort, cross-sectional and case–control human studies with a follow-up period of at least 6 months comparing two groups of patients with presence or absence of KM, or with KM < 2 mm or ≥2 mm were included. Primary outcomes were implant failures, PROMs and BoP (BoP/mBI). Additional outcomes were PPD, plaque accumulation (mPI/PI), gingival inflammation (GI/mGI), marginal bone loss (MBL), soft tissue recession (REC) and biological complications. Results: Fifteen studies were included (one RCT, two cohort prospective and twelve cross-sectional). Meta-analysis was performed for cross-sectional studies. Implant failure and complications were not presented as outcome measures, and five studies analyzed PROMs. Results from the meta-analysis reported no evidence of any statistical significant difference between groups in PPD, BoP and MBL, while a statistical significant difference in GI/BI, PI and REC was present in favor of the group with KW ≥ 2 mm. More biological complications were present in the group with no KM/KM < 2 mm but few cases were present to draw any conclusions. Although a meta-analysis could not be performed, a consistent trend toward the worst pain/discomfort in KM < 2 mm was observed. Conclusions: No clear evidence was found supporting the role of KM in peri-implant health and PROMs, even if more plaque and marginal inflammation were present in the KM < 2 mm group. Clinical relevance: KM could have a role in patients with erratic maintenance and patient comfort. Full article

Top seal failure of ram blowout preventer (BOP) is one of the main factors leading to well control risk. The constitutive model and parameters of nitrile butadiene rubber (NBR) were optimized by compression and tensile tests, and the failure analysis model of the contact seal of the ram BOP top seal was built. The nonlinear contact mechanical behavior of the connection part of the BOP top seal was analyzed by the finite element method. Then, the influence of corrosion and wear defects at the top seal position of the 2FZ35-70 BOP under rated working pressure on the contact seal were studied, and the results showed that the overall contact pressure distribution of the top seal corrosion defects was uniform, the local contact pressure of the corrosion pit edge increased, and the top contact pressure decreased. The overall contact pressure of the wear defect of the top seal decreased linearly, the contact pressure at the maximum depth of the wear defect was the smallest, and the contact pressure gradually decreased to both sides. Ultimately, to guarantee the safety and reliability of the ram BOP, it is suggested that the acceptable depths of the seal corrosion pit and the wear at the top of the ram BOP are 4.0 mm and 0.2 mm, respectively, thus the reliability evaluation problem of the quantitative seal of the ram BOP top seal is solved. Full article

Background: The present study aims to analyze the use of Laser-Lok microtextured neck implants placed with a transmucosal surgical approach. The marginal bone level (MBL) and periodontal parameters were evaluated in a cohort prospective 4-year clinical study. Methods: A total of 41 implants were placed in 36 healthy consecutive patients (16 males, 20 females, mean age 60 ± 9 years). Tapered tissue level implants, characterized by a 2.0 mm laser-microtextured neck, were used with a flapless approach. Customized abutments and provisional resin crowns were positioned. Definitive metal–ceramic crowns were cemented approximately 4 months after insertion. Periapical radiographs were taken after 1, 3, 6, 12, 36 and 48 months from implant placement to evaluate MBL. Gingival thickness (thin/thick), plaque score (PS) and bleeding on probing (BoP) were evaluated. Results: After 48 months, all implants were safe from complications. No complications, peri-implantitis, early implant failures or mucositis occurred. The survival rate was 100%. Mean MBL during the follow-up was −0.15 ± 0.18 at T1, −0.29 ± 0.29 at T3, −0.45 ± 0.37 at T6, −0.53 ± 0.45 at T12, −1.06 ± 1.13 at T 36 and −1.10 ± 0.89 at T 48. Implants placed 2–3 months after tooth extraction revealed lower MBL variation when compared to those placed immediately (in fresh extraction sockets) or in completely healed ridges (delayed group). Narrower diameter implants (3.8 mm) showed significantly higher MBL variation when compared to 4.6 diameter implants. Multilevel analysis at T48 revealed that among all the evaluated variables, implant diameter was the factor mostly associated with MBL modifications (p = 0.027). Conclusion: This 4-year clinical study supports the use of Laser-Lok implants placed at tissue level with a flapless approach. A limited bone loss during the 48-month follow-up was observed. Periodontal parameters were stable with no sign of inflammation or soft tissue alteration. The use of Laser-Lok implants with transmucosal surgery represents a suitable technique with a minimally invasive approach. Full article

The subsea wellhead (SW) system is a crucial connection between blowout preventors (BOPs) and subsea oil and gas wells. Excited by cyclical fatigue dynamic loadings, the SW is prone to fatigue failure, which would lead to the loss of well integrity and catastrophic accidents. Based on the Bayesian Regularization Artificial Neuron Network (BRANN), this paper proposes an efficient probability approach to predict the fatigue failure probability of SW during its entire life. In the proposed method, the BRANN fatigue damage (BRANN-FD) model reflecting the non-linear relationship between the input and output data was developed by the limited fatigue damage analysis data, which was utilized to generate thousands of non-numerical fatigue damage data of SW rapidly. Combining parametric and non-parametric estimation methods, the probability density function (PDF) of SW fatigue damage was determined to calculate the accumulation fatigue damage during service life. Using the logistic regression, the fatigue failure probability of SW was predicted. The application of the proposed approach was demonstrated by a case study. The results illustrated that the fatigue damage of SW would be viewed as obeying the Lognormal distribution, which could be used to obtain the accumulation fatigue damage in operation conveniently. Furthermore, the fatigue failure probability of SW nonlinearly increased with the increment in the accumulation fatigue damage of SW, which could be helpful to ensure the operation safety of SW in deepwater oil and gas development, especially for aged wellhead. Full article

(1) Background: Most of the clinical literature dealing with dental implants has been issued by experienced teams working either in university settings or in private practice. The purpose of this study was to identify contributing covariates to implant failure and marginal bone loss (MBL) at the 1-year follow-up of a novel triangular-neck implant design when placed by inexperienced post-graduate students. (2) Methods: A prospective cohort study was conducted on study participants eligible for implant placement at the UIC (International University of Catalonia), Barcelona, Spain. Implant failure rate and contributors to implant failure and MBL were investigated among 24 implant and patient variables. (3) Results: One hundred and twenty implants (V3, MIS) were placed and rehabilitated by the students. The mean insertion torque was 37.1 Ncm. Survival and success rates were 97.5% and 96.7%, respectively. Implants placed in patients with smoking habits displayed a tendency of higher failure risk (OR = 5.31, p = 0.17) when compared to non-smokers. The mean (SD) MBL was 0.51 (0.44) mm. Gender significantly affected the MBL (p = 0.020). Bleeding on probing (BoP) on the buccal sites proved to be a good predictor of proximal MBL (p = 0.030). (4) Conclusions: The survival and success rates of the V3 triangular-neck implant placed by inexperienced post-graduate students at the 1-year follow-up were high and similar to the ones published in the literature by experienced teams on other implants. Full article

An important market that is receiving increasing attention by firms relates to the poorest at the Base of the Pyramid (BoP). BoP businesses contribute to the first UN Sustainable Development Goal that calls for an end to poverty in all its manifestations. BoP businesses are regarded as financially and socially beneficial for both participating firms and poor communities. It is, however, understood that success in BoP markets cannot (and should not) be assumed, as it demands a profoundly different view towards managing supply chains. Focusing on this issue, our conceptual study contributes to the emerging debates in BoP and supply chain management research by elaborating the notion of legitimacy contexts (LCs) at BoP. We draw on institutional theory to characterize the LCs in BoP markets and discuss their implications for key supply chain functions. We argue that firms often design their supply chain functions for BoP business using their own LCs as opposed to those of BoP actors. This implies ignoring the institutional distance between BoP markets and firms and reveals a key culprit in the failure of BoP projects. We offer practical implications for firms intending to engage in BoP business. Full article

End-stage renal failure is the reason for complications in many systems and organs, and the applied pharmacotherapy often causes the deepening of already existing pathologies within the oral cavity, such as: caries, periodontal diseases, mucosal lesions or reduced saliva secretion. Reduced saliva secretion results in an increased accumulation of dental plaque, its mineralization and prolonged retention, which leads to the development of gingival and periodontal inflammation. There is some evidence that chronic kidney diseases are influenced by periodontal health. The aim of the work was to evaluate the dental needs by the usage of clinical assessment of periodontal tissues of patients suffering from end-stage chronic kidney disease, arterial hypertension or/and diabetes mellitus. Material and methods: 228 patients underwent the research. 180 patients were hemodialized in Diaverum dialysis stations (42 of them were diagnosed with end stage chronic disease, 79 with the end stage chronic disease and arterial hypertension, 16 with end stage chronic kidney disease and diabetes, 43 with end-stage chronic disease, arterial hypertension and diabetes) and 48 patients of the Conservative Dentistry with Endodontics Clinic of Academic Centre of Dentistry of Silesian Medical University in Bytom and patients of the dentistry division of Arnika Clinic in Zabrze not diagnosed with any of the aforementioned diseases. The scheme of the research comprised 2 parts: analysis of the general health and assessment of the periodontal status which contain the following indices: Periodontal Probing Depth (PPD), Clinical Attachment Lost (CAL), Bleeding Index or Bleeding on Probing Index (BI or BOP), Community Periodontal Index for Treatment Needs (CPITN). Results: Significantly lower percentage of patients with healthy periodontal tissues and higher percentage with periodontal pockets deeper than 3.5 mm and the loss of trainers connective of 5 mm or higher were in the examined group. The values of the bleeding index were significantly lower in control group. The analysis of the CPITN index indicates higher percentage of patients qualified as CPI 1 or 2 in the control group while in the examined one most of the patients turned out to require specialist periodontal treatment. Conclusions: there is a direct relationship between periodontal status and end-stage renal disease which typically includes other chronical civilization ailments. It is important to develop a scheme for the easy and rapid examination of periodontal status, to determine the treatment needs in this area, which will allow precise assignment of long-term dialyzed patients to the range of prophylactic and therapeutic procedures. Full article

The progressive increase in hydrogen technologies’ role in transport, mobility, electrical microgrids, and even in residential applications, as well as in other sectors is expected. However, to achieve it, it is necessary to focus efforts on improving features of hydrogen-based systems, such as efficiency, start-up time, lifespan, and operating power range, among others. A key sector in the development of hydrogen technology is its production, renewable if possible, with the objective to obtain increasingly efficient, lightweight, and durable electrolyzers. For this, scientific works are currently being produced on stacks technology improvement (mainly based on two technologies: polymer electrolyte membrane (PEM) and alkaline) and on the balance of plant (BoP) or the industrial plant (its size depends on the power of the electrolyzer) that runs the stack for its best performance. PEM technology offers distinct advantages, apart from the high cost of its components, its durability that is not yet guaranteed and the availability in the MW range. Therefore, there is an open field of research for achievements in this technology. The two elements to improve are the stacks and BoP, also bearing in mind that improving BoP will positively affect the stack operation. This paper develops the design, implementation, and practical experimentation of a BoP for a medium-size PEM electrolyzer. It is based on the realization of the optimal design of the BoP, paying special attention to the subsystems that comprise it: the power supply subsystem, water management subsystem, hydrogen production subsystem, cooling subsystem, and control subsystem. Based on this, a control logic has been developed that guarantees efficient and safe operation. Experimental results validate the designed control logic in various operating cases, including warning and failure cases. Additionally, the experimental results show the correct operation in the different states of the plant, analyzing the evolution of the hydrogen flow pressure and temperature. The capacity of the developed PEM electrolysis plant is probed regarding its production rate, wide operating power range, reduced pressurization time, and high efficiency. Full article

Pocket probing depth (PPD) and bleeding on probing (BOP) measurements are useful indices for the assessment of periodontal conditions. The same periodontal indices are commonly recommended to evaluate the dental implant/tissue interface to identify sites with mucositis and peri-implantitis, which, if not treated, are anticipated to lead to implant failure. The aim of the present narrative review is to discuss the available literature on the effectiveness of probing at dental implants for identification of peri-implant pathology. There is substantial clinical evidence that PPD and BOP measurements are very poor indices of peri-implant tissue conditions and are questionable surrogate endpoints for implant failure. On the contrary, the literature suggests that frequent disturbance of the soft tissue barrier at implants may instead induce inflammation and bone resorption. Moreover, over-diagnosis and subsequent unnecessary treatment may lead to iatrogenic damage to the implant-tissue interface. Despite this, the recommendations from recent consensus meetings are still promoting the use of probing at dental implants. For evaluation of implants, for instance at annual check-ups, the present authors recommend a clinical examination that includes (i) a visual inspection of the peri-implant tissues for the assessment of oral hygiene and the detection of potential redness, swelling, (ii) palpation of the peri-implant tissues for assessment of the potential presence of swelling, bleeding, suppuration. In addition, (iii) radiography is recommended for the assessment of crestal bone level for comparison with previous radiographs to evaluate potential progressive bone loss even if there is a need for more scientific evidence of the true value of the first two clinical testing modes. Full article